1. Field of the Invention
The present invention relates to an information distribution system, information processing device and memory medium, and more particularly to an information distribution system, information processing device and memory medium that record contents (shared information), such as a movie that is to be shared among a plurality of information processing devices, in a plurality of information processing devices of the information distribution system before making the contents public so they can be shared.
2. Discussion of the Related Art
Recently, much research and development is being performed of a system in which a terminal device (node) is used to access a server or the like that stores contents such as mentioned above via an network such as the Internet, and having contents desired for viewing at that node distributed to that node and viewed, or in other words, a so-called contents distribution system.
Also, as an example of that kind of distribution system is a distribution system in which the contents are directly exchanged between nodes of a network, for example, there is a P2P (Peer-to-Peer) type distribution system, which is a distribution system in which the contents are distributed among a plurality of nodes, and the contents are shared by the plurality of nodes. The aim of this kind of P2P type of distribution system is to solve the problems of concentrated access of a server and high management costs that are disadvantages of a conventional client-server type model.
Moreover, in the research being done in this field, in Peer-to-Peer, for example, in an overlay network that is logically created using a distributed hash table (hereafter, referred to as DHT), the nodes do not recognize the link information (for example, IP address) of all of the nodes that participate in that overlay network, and contains only link information for part of the nodes that is obtained when participating, and performs data inquiries based on that link information.
In this kind of overlay network, load distribution must be adequately performed even when node participation and withdrawal (separation) are performed frequently, and the non-patent document. “Lightweight Load Balancing for Distributed Hash Table”, Technical Report of The Institute of Electronics Information and Communication Engineers, discloses a technique for adequately performing load distribution in an overlay network even when participation and withdrawal (separation) are performed frequently. Moreover, distributing copies (replicas) of the contents among a plurality of nodes and having a node keep those contents is effective in avoiding concentrated access of certain nodes, and prior proposals related to the creation and placement of replicas are disclosed for example in Japanese patent application 2003-99337 and Japanese patent application 2003-216521.
Japanese patent application 2003-99337 discloses a method of creating and placing replicas (copies) with good balance over an entire network within a service group by referencing the overall size (overall amount of information) and number of contents that exist at each of the nodes that are connected within that service group of a network.
Furthermore, Japanese patent application 2003-216521 discloses a method of inserting parameters such as level of importance into each of the contents, and creating many replicas of popular contents.
[Non-Patent Document 1]
    “Lightweight Load Balancing for Distributed Hash Tables”, Technical Report of The Institute of Electronics Information and Communication Engineers[Patent Document 1]    Japanese patent application 2003-99337[Patent Document 2]    Japanese patent application 2003-216521